During past years, several network operators around the world have introduced personalized RingBack Tone (RBT) services. Such a service enables a subscriber to choose a custom audio clip (e.g., a favorite song) to be played back to a caller phone during a ringing portion of a call, prior to the subscriber answering the call. Thus, instead of hearing a standard ring-back tone (at the caller phone) indicating that a target phone is being alerted of the incoming call connection request, the caller hears the custom audio clip selected by the subscriber.
According to one conventional application, a subscriber of the custom ring-back tone service may specify one of several audio clips to be played by a respective phone switch network based on caller identification, time-of-day, or other factors. The purpose of the audio clip can be entertainment, advertising, or corporate identification/branding.
A conventional architecture for providing custom ring-back tones includes a Mobile Switching Center (MSC), a Home Location Register (HLR), and a ring-back tone generator. In this architecture, software in a network operator's MSC, in conjunction with the Home Location Register (HLR), identifies which received calls have been placed to corresponding subscribers of the ring-back service. For such calls, the MSC sets up a voice path to the ring-back tone generator for conveying a ring-back tone to the caller phone while also placing an outbound call connection to alert the subscriber of the call placed by the caller phone. The ring-back tone generator then plays the selected audio clip back to the caller through the voice path while the subscriber phone is alerted of the incoming call connection request. When the MSC detects that the subscriber answers his alerting phone, or the target phone abandons the call, the MSC releases the voice path to the ring-back tone generator and continues on with normal call handling. For example, after detecting that the subscriber answers his phone, the MSC breaks a link to the ring-back tone generator and bridges the caller phone to the subscriber phone via a voice communication channel so that the subscriber and the caller can talk with each other without the custom ring-back tone being played.